The museum's atrium features vehicles used to deliver mail throughout the history of the USPS, including
planes,
trains and
automobiles. Historical exhibits guide visitors through the postal service's inception and expansion, as well as its role in significant national events such as
World War II. "Systems at Work" explores historic and current technologies involved in mail processing and delivery, such as
message boxes,
ZIP codes,
optical scanners and
conveyor systems. The museum holds the
National Philatelic Collection. The museum has a gift shop and a United States Postal Service philatelic sales window. Admission is free. In 2005, the museum acquired the childhood stamp collection of the late singer/songwriter
John Lennon. From June 2015 until December 2019, the museum displayed the 1856
British Guiana 1c magenta, the world's most valuable stamp, which sold for nearly $10 million. In September 2009, the museum received an $8 million gift from investment firm founder
William H. Gross to help finance an expansion project. The William H. Gross Stamp Gallery of the museum is named in his honor. ==Events==